Reuben heard.

Genesis 35:22
While Israel was living in that region, Reuben went in and slept with his father's concubine Bilhah, and Israel heard about it. Jacob had twelve sons:

Genesis 42:22
But Reuben replied: "Didn't I tell you not to sin against the boy? But you would not listen. Now we must account for his blood!"

not kill him.

Joshua 10:28
On that day Joshua captured Makkedah and struck it down with the sword, along with its king. He completely destroyed it and everyone in it, leaving no survivors. So he did to the king of Makkedah as he had done to the king of Jericho.

Genesis 9:5
And surely I will require the life of any man or beast by whose hand your lifeblood is shed. I will demand an accounting from anyone who takes the life of his fellow man:

Matthew 10:28
Do not be afraid of those who kill the body but cannot kill the soul. Instead, fear the One who can destroy both soul and body in hell.